if you can get a letter from his school teacher, headmaster, local priest, doctor ? stating you are responsible for all of the important issues in the child's life that will help.
for the school just mention that it was you who took him to school each day, paid his fees,
a letter from the local church would help showing you was responsible for the child's spiritual beliefs. one from his local doctor stating that it was you who took him for treatment for xx years,
